strtok: #include <string.h> char *strtok(char *str, const char *delim); char *strtok_r(char *str, const char *delim, char **saveptr); 功能：分解字符串为一组标记串。str为要分解的字符串，delim为分隔符字符串。 说明：首次调用时，str必须指向要分解的字符串，随后调用要把s设成NULL。 strtok在str中查找包含在delim中的字符并用NULL('/0')来替换，直到找遍整个字符串。 返回指向下一个标记串。当没有标记串时则返回空字符NULL。 实例：用strtok来判断ip地址是否合法：ip_strtok.c： [c-sharp] view plaincopy //ip_strtok.c #include <stdio.h> #include <string.h> int main(int argc, char **argv) { char temp_buf[100] = {}; char p_temp[100]; char *p=NULL; char *t = "."; int m,n,i; int j=0,s=0; if(argc!=2) { printf("param must 2/n"); return -1; } strcpy(temp_buf, argv[1]); for(i=0; i<strlen(temp_buf);i++) { if(temp_buf[i] == *t)j++; if(temp_buf[i] == *t && (temp_buf[i+1]>='0'&&temp_buf[i+1]<='9')) { s++; } } if(j!=3 || j!=s) { printf("ip param format error/n"); return -1; } p = strtok(temp_buf, t); while(p!=NULL) { strcpy(p_temp, p); printf("%s /n", p_temp); for(n=0; n<strlen(p_temp);n++) { if(!(p_temp[n]>='0'&&p_temp[n]<='9')) { printf("ip param error/n"); return -1; } } m = atoi(p_temp); if(m>255) { printf("ip invalid /n"); return -1; } p=strtok(NULL, "."); printf("p = %s/n",p); } printf("ok! ip correct! ip=%s/n", argv[1]); return 0; } 编译运行： [root@localhost liuxltest]# uname -r 2.6.26 [root@localhost liuxltest]# gcc -Wall ip_strtok.c -o ip_strtok [root@localhost liuxltest]# ./ip_strtok 172.18.4.255 172 p = 18 18 p = 4 4 p = 255 255 p = (null) ok! ip correct! ip=172.18.4.255 [root@localhost liuxltest]# ./ip_strtok 172.18. ip param format error strtok实现函数： xl_strtok.c [c-sharp] view plaincopy #include <string.h> #include <stdio.h> #include <stdlib.h> char *xl_strtok(char *str, const char *delim); int main(int argc, char **argv) { if(argc != 3) { printf("param must be 3 /n"); return -1; } char *temp; char *p_temp; char *p; temp=(char *)malloc(100); p_temp=(char *)malloc(100); strcpy(temp, argv[1]); strcpy(p_temp, argv[2]); printf("temp = %s /n",temp); printf("p_temp = %s /n", p_temp); p = xl_strtok(temp, p_temp); printf("%s/n", p); return 0; } char *xl_strtok(char *s, const char *dm) { static char *last; char *tok; if(s == NULL) s = last; if(s == NULL) return NULL; tok = s; while (*s != '/0') { while (*dm) { if (*s == *dm) { *s = '/0'; last = s + 1; break; } s++; } } return tok; } strtok源码： /*********************************************************************/ /*** *strtok.c - tokenize a string with given delimiters * * Copyright (c) Microsoft Corporation. All rights reserved. * *Purpose: * defines strtok() - breaks string into series of token * via repeated calls. * *******************************************************************************/ #include <cruntime.h> #include <string.h> #ifdef _SECURE_VERSION #include <internal.h> #else /* _SECURE_VERSION */ #include <mtdll.h> #endif /* _SECURE_VERSION */ /*** *char *strtok(string, control) - tokenize string with delimiter in control * *Purpose: * strtok considers the string to consist of a sequence of zero or more * text tokens separated by spans of one or more control chars. the first * call, with string specified, returns a pointer to the first char of the * first token, and will write a null char into string immediately * following the returned token. subsequent calls with zero for the first * argument (string) will work thru the string until no tokens remain. the * control string may be different from call to call. when no tokens remain * in string a NULL pointer is returned. remember the control chars with a * bit map, one bit per ascii char. the null char is always a control char. * *Entry: * char *string - string to tokenize, or NULL to get next token * char *control - string of characters to use as delimiters * *Exit: * returns pointer to first token in string, or if string * was NULL, to next token * returns NULL when no more tokens remain. * *Uses: * *Exceptions: * *******************************************************************************/ #ifdef _SECURE_VERSION #define _TOKEN *context #else /* _SECURE_VERSION */ #define _TOKEN ptd->_token #endif /* _SECURE_VERSION */ #ifdef _SECURE_VERSION char * __cdecl strtok_s ( char * string, const char * control, char ** context ) #else /* _SECURE_VERSION */ char * __cdecl strtok ( char * string, const char * control ) #endif /* _SECURE_VERSION */ { unsigned char *str; const unsigned char *ctrl = control; unsigned char map[32]; int count; #ifdef _SECURE_VERSION /* validation section */ _VALIDATE_RETURN(context != NULL, EINVAL, NULL); _VALIDATE_RETURN(string != NULL || *context != NULL, EINVAL, NULL); _VALIDATE_RETURN(control != NULL, EINVAL, NULL); /* no static storage is needed for the secure version */ #else /* _SECURE_VERSION */ _ptiddata ptd = _getptd(); #endif /* _SECURE_VERSION */ /* Clear control map */ for (count = 0; count < 32; count++) map[count] = 0; /* Set bits in delimiter table */ do { map[*ctrl >> 3] |= (1 << (*ctrl & 7)); } while (*ctrl++); /* Initialize str */ /* If string is NULL, set str to the saved * pointer (i.e., continue breaking tokens out of the string * from the last strtok call) */ if (string) str = string; else str = _TOKEN; /* Find beginning of token (skip over leading delimiters). Note that * there is no token iff this loop sets str to point to the terminal * null (*str == '/0') */ while ( (map[*str >> 3] & (1 << (*str & 7))) && *str ) str++; string = str; /* Find the end of the token. If it is not the end of the string, * put a null there. */ for ( ; *str ; str++ ) if ( map[*str >> 3] & (1 << (*str & 7)) ) { *str++ = '/0'; break; } /* Update nextoken (or the corresponding field in the per-thread data * structure */ _TOKEN = str; /* Determine if a token has been found. */ if ( string == str ) return NULL; else return string; }